The goal of our research is to bridge the gap between basic research in cochlear physiology and clinical tools in otology such as otoacoustic emissions and cochlear implants. We will use a combination of experimental and theoretical techniques to develop comprehensive computer models of cochlear function. The experimental work is specifically designed to generate detailed data sets that can be used for model parameter estimation and model validation. Our project specifically focuses on how the electrical and mechanical properties of the cochlea, both active and passive, result in the extremely sensitive responses observed in inner hair cells (IHC) and auditory-nerve (AN) fibers. The models to be developed will be used to integrate a wide range of experimental data as well as to simulate changes in otoacoustic emissions due to cochlear pathology and to simulate the electric fields produced by cochlear implants. We will address four fundamental questions: 1) How does the architecture of the organ of Corti determine the passive mechanical properties of the cochlea? 2) How do outer hair cell (OHC) electromechanical properties lead to cochlear amplification? 3) What are the mechanisms that drive and distribute ionic current flow throughout the cochlea? 4) Where and how are otoacoustic emissions produced in the cochlea? To answer these questions, we will use a combination of experimental and theoretical techniques to study the mechanical and electrical properties of the gerbil and the human cochlea. We will develop detailed finite element hydromechanical and electroanatomical models of the cochlea, as well as an integrated finite-difference model for the cochlear amplifier that incorporates both the hydromechanical properties and the electroanatomical properties of the cochlea. These models will allow us to simulate the intrinsic current flows that lead to clinically important field potentials such as the cochlear microphonic (CM), summating potential (SP) and the compound action potential (CAP), as well as to create tools that can be used to predict the effects of artificial currents such as those produced by cochlear implants. The models to be developed can also be used to interpret emission data from normal and diseased ears. This research will lead to new insights into the relationship between changes in clinically important diagnostic measures such as otoacoustic emissions and underlying cochlear pathologies. It will also aid in the design and fitting of cochlear implants.